JMAP for Calendars, Contacts and Files Now in Stalwart

I can understand why JMAP instead of IMAP given the latter's antiquated design. I don't see the advantage to clients in replacing WebDAV though, and the others are a bit iffy too. They'll need to make a way better sales pitch than 'JSON vs XML' (serialization ain't tough, XML is supported everywhere).

I guess contacts/calendar follows JMAP naturally when the clients already implement it, but that only applies in the 'already wrote a JMAP email client' case. Virtually any other case would rather stay with widely supported protocols?